Ammotrypanella cirrosa Schüller, 2008, sp. nov.

Ammotrypanella cirrosa sp. nov.

(Fig. 3A–B)

Holotype. ANDEEP I–II, Weddell Sea, Antarctic Peninsula, Sta. 131-3, 0 5 March 2002, 65°19.83’S, 51°31.62’W, 3049–3050 m, EBS, ZMH P- 24751.

Paratypes. ANDEEP I–II; Weddell Sea, Antarctic Peninsula, Sta. 131-3, 0 5 March 2002, 65°19.83’S, 51°31.62’W, 3049–3050 m, EBS, 63 specimens, ZMH P- 24752.

Additional material. 42-2 (4), 134-4 (2), 141-10 (1), 16-10 (6), 59-5 (2), 78-9 (2), 102-13 (4), 110-8 (1), 121-11 (40), 153-7 (4), 154-9 (1).

Etymology. The name refers to the presence of numerous small cirri and a large ventral cirrus on the posterior margin of the anal tube.

Diagnosis. The species can be recognized by the presence of a thick ventral cirrus and numerous small cirri on the posterior margin of the anal tube.

Description. Holotype complete, body long and thin, 16 mm long and 1.5 mm wide for 40 chaetigers.

A median species of 7–25 mm length and 0.5–2 mm width; number of chaetigers 37–42. Ventral groove present along whole length of body. Posterior body region bilaterally flattened. Color in alcohol white to a light tan.

Prostomium conical ending in a short palpode. Peristomium indistinct, a thin ring around the lips. First subsequent segment without chaetae. Nuchal organs apparent as narrow grooves laterally, eyes absent (Fig. 3A).

Anterior 7–8 parapodia button shaped, chaetae long, stiff, in bushy fascicles. Median parapodia embedded in lateral groove, becoming more distinct in posterior part of body; posterior chaetae long and straight. All chaetae simple.

Branchiae flat with wide base, tapering to top; all of similar length; present in region from chaetigers 23– 31, exact number variable.

Posterior chaetigers shorter, close to each other. Pygidium with anal tube; length of anal tube about that of last 5–8 chaetigers; posterior margin with few short cirri; ventral cirrus robust, about half the length of anal tube (Fig. 3B).

Remarks. The species is most similar to Ammotrypanella arctica. The most apparent diagnostic difference is the presence of a robust ventral cirrus on the anterior margin of the anal tube. Other than that the anal tube is very similar to that of A. arctica and recognition of this species becomes difficult when the ventral cirrus is lost. In that case the structure of the branchiae can be considered, as they are less flattened and more robust than in A. arctica.

Distribution. Atlantic sector of Southern Ocean and Antarctic Peninsula, 2014–4817 m